Method for cleaning electrostatic chuck

ABSTRACT

A method includes emitting, by a first portion of an optical inspection instrument, a radiation toward a supporting surface of a chuck, wherein the chuck is configured for fixing a semiconductor workpiece on the supporting surface, and the optical inspection instrument faces the supporting surface; receiving, by a second portion of the optical inspection instrument, a reflection of the radiation reflected from the chuck; analyzing the reflection of the radiation; determining whether a particle is present on the supporting surface of the chuck based on the analyzing the reflection of the radiation; and removing the particle by using a cleaning tool comprising an exhaust duct.

PRIORITY CLAIM AND CROSS-REFERENCE

This present application is a continuation application of U.S. patentapplication Ser. No. 17/991,724, filed on Nov. 21, 2022, which is acontinuation application of U.S. patent application Ser. No. 17/365,878,filed on Jul. 1, 2021, now U.S. Pat. No. 11,508,602, issued on Nov. 22,2022, which is a divisional application of U.S. patent application Ser.No. 16/358,561, filed on Mar. 19, 2019, now U.S. Pat. No. 11,056,371,issued on Jul. 6, 2021, which claims priority to U.S. provisionalapplication Ser. No. 62/718,947, filed on Aug. 14, 2018, all of whichare herein incorporated by reference in their entirety.

BACKGROUND

The semiconductor integrated circuit (IC) industry has experiencedexponential growth. Technological advances in IC materials and designshave produced generations of ICs in which each generation has smallerand more complex circuits than the previous generation. However, theminimum feature size that may be patterned by the semiconductorlithography processes is substantially limited by the wavelength of theprojected radiation source. In order to improve the feature size to beeven smaller than before, an extreme ultraviolet (EUV) radiation sourceand related semiconductor lithography processes have been introduced.During the EUV semiconductor lithography processes, an electrostaticchuck (also known as an R-chuck, an E-chuck, or an ESC) is configured tohold a reflection-type mask through electrostatic forces, such that theEUV semiconductor lithography processes may optically transfer patternsof the reflection-type mask onto a wafer.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 is a schematic diagram illustrating a front view of anelectrostatic chuck cleaning tool in accordance with some embodiments ofthe present disclosure.

FIGS. 2A and 3A are schematic diagrams illustrating an opticalinspection instrument of the electrostatic chuck cleaning tool inaccordance with some embodiments of the present disclosure.

FIGS. 2B and 3B are line charts depicted according to FIGS. 2A and 3A,respectively.

FIGS. 4-6 are schematic diagrams illustrating front views of anelectrostatic chuck cleaning tool in accordance with some otherembodiments of the present disclosure.

FIGS. 7A-7C are schematic diagrams illustrating various cleaning pathsof the electrostatic chuck cleaning tool in accordance with someembodiments of the present disclosure.

FIG. 8 is a flow chart illustrating a method for cleaning particle on anelectrostatic chuck in accordance with some embodiments of the presentdisclosure.

FIG. 9 is a flow chart of the operation S10 b in FIG. 8 in accordancewith some embodiments of the present disclosure.

FIG. 10 is a flow chart illustrating a method for cleaning particle onan electrostatic chuck in accordance with some other embodiments of thepresent disclosure.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one component or feature's relationship toanother component(s) or feature(s) as illustrated in the figures. Thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. The apparatus may be otherwiseoriented (rotated 90 degrees or at other orientations) and the spatiallyrelative descriptors used herein may likewise be interpretedaccordingly.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this disclosure belongs. It willbe further understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art and thepresent disclosure, and will not be interpreted in an idealized oroverly formal sense unless expressly so defined herein.

As used herein, “around,” “about,” “substantially” or “approximately”shall generally mean within 20 percent, within 10 percent, or within 5percent of a given value or range. Numerical quantities given herein areapproximate, meaning that the term “around,” “about,” “substantially” or“approximately” can be inferred if not expressly stated.

An EUV semiconductor lithography process may utilize a plurality ofmirrors and a reflection-type photomask (or referred to as a mask or areticle) to form a pattern from the reflection-type mask onto a targetwafer. In detail, a backside of the reflection-type photomask isreleasably attached onto an electrostatic chuck through an electrostaticforce. However, contamination (for example, tiny particle contamination)may occur on the electrostatic chuck, and more particularly, on asurface of the electrostatic chuck that contacts the backside of thereflection-type photomask. Hence, the aforementioned contamination mayresult in various issues, e.g., photomask deformation, so that thepattern on the reflection-type photomask may not be faithfullytransferred onto the target wafer, resulting in deterioration in theperformance of the wafer. Consequently, in an effort to adequatelyaddress these issues, an electrostatic chuck cleaning tool and anelectrostatic chuck cleaning method are presented hereinafter inaccordance with various embodiments of the present disclosure.

Reference is made to FIG. 1 , which is a schematic diagram illustratinga front view of an electrostatic chuck cleaning tool 100 in accordancewith some embodiments of the present disclosure. As shown in FIG. 1 ,the electrostatic chuck cleaning tool 100 includes a platform 110, aspindle 120, a motor 130, a casing 140, height sensors 150, and a vacuumsource 160. The platform 110 has a sidewall 112 and a top surface 114.The spindle 120 is connected between the platform 110 and the motor 130.The casing 140 is disposed around and spaced apart from the sidewall 112and the spindle 120, such that an exhaust duct 142 is definedtherebetween. The height sensors 150 are located on the casing 140. Thevacuum source 160 is connected to the exhaust duct 142. Therefore, theplatform 110 may release a particle(s) P from the electrostatic chuckESC through various methods that will be discussed below, and the vacuumsource 160 may draw the particle P into the exhaust duct 142.

As shown in FIG. 1 , protrusions PT on the electrostatic chuck ESC thatcontact a backside of a photomask may be referred to as mesas, bumps,pins, islands, surface structures, or the like. Further, multiplechannels CN such as grooves and recesses may be formed between theprotrusions PT for allowing fluid to flow therein. The channels CN maybe fluidly coupled to a source of a thermally conductive fluid, such ashelium (He) gas. Hence, the thermally conductive fluid may be providedat controlled pressure into the channels CN, so as to enhance the heattransfer between the electrostatic chuck ESC and the photomask.Additionally, when the photomask is held by the electrostatic chuck ESC,the protrusions PT may be in direct contact with the photomask. In themeantime, if particles P exist at the contact region between theelectrostatic chuck ESC and the photomask, these particles P might leadto adverse impact, such as particle-induced distortion on the photomask.

As shown in FIG. 1 , the platform 110, the spindle 120, and the motor130 are connected in this sequence, i.e., these components are arrangedfrom top to bottom. The motor 130 may rotate the platform 110 throughthe spindle 120. In some embodiments, the motor 130 may move theplatform 110 toward the electrostatic chuck ESC and may refrain fromrotating the platform 110 until the platform 110 is spaced apart fromthe electrostatic chuck ESC by a distance D1, in which the distance D1may be in a range from about 100 μm to about 10 nm. If the distance D1is greater than about 100 um, the platform 110 may not interact with theparticle P. If the distance is smaller than about 10 nm, collisionbetween the platform 110 and the electrostatic chuck ESC may occur. Insome embodiments, when the platform 110 starts to be rotated, thedistance D1 is kept substantially constant and within the aforementionedrange, such that the platform 110 may be spaced apart from theelectrostatic chuck ESC by an appropriate distance that prevents theplatform 110 from colliding with the electrostatic chuck ESC.Additionally, the sidewall 112 and/or the top surface 114 of theplatform 110 may be in direct contact with the particle P withoutcontacting the electrostatic chuck ESC, such that the particle P may bephysically released from the electrostatic chuck ESC through therotation of the platform 110.

As shown in FIG. 1 , the motor 130 is located at the lowermost positioncompared with other components of the electrostatic chuck cleaning tool100, such that these components may be arbitrarily moved along with themotor 130. More specifically, in addition to rotating the platform 110,the motor 130 may also move the platform 110 along a first direction 132and a second direction 134 with respect to the electrostatic chuck ESC,in which the first direction 132 and the second direction 134 areperpendicular to each other. For example, the platform 110 may approachthe electrostatic chuck ESC through decreasing the distance D1 along thefirst direction 132. As another example, when the platform 110 isrotated and spaced apart from the electrostatic chuck ESC by anappropriate distance, the platform 110 may be moved along the seconddirection 134 for cleaning more areas or different regions on theelectrostatic chuck ESC. Additionally, the motor 130 may also move theplatform 110 along a direction which is perpendicular to both the firstdirection 132 and the second direction 134. Hence, the motor 130 mayoperate to realize three-dimensional movement of the platform 110 withrespect to the electrostatic chuck ESC, i.e., the platform 110 may bemoved along a vertical direction and/or a horizontal direction withrespect to the electrostatic chuck ESC.

As shown in FIG. 1 , the casing 140 may enclose the sidewall 112 and thespindle 120 while the top surface 114 is exposed, such that afunnel-shaped casing may be provided to cover portions of theelectrostatic chuck cleaning tool 100. In some embodiments, the contourof the casing 140 is substantially conformal to that of the sidewall 112and the spindle 120. Hence, an exhaust duct 142 may be defined betweenthe casing 140 and the covered portions of the electrostatic chuckcleaning tool 100. The exhaust duct 142 may draw the particle P releasedfrom the electrostatic chuck ESC. In some embodiments, the casing 140may further enclose other components like the motor 130. In someembodiments, an uppermost portion of the casing 140 is substantiallycoplanar with the top surface 114 of the platform 110, such thataccidental collision of the casing 140 with the electrostatic chuck ESCis prevented. In some embodiments, the uppermost portion of the casing140 may be lower than the top surface 114 of the platform 110 forfurther preventing the accidental collision of the casing 140 with theelectrostatic chuck ESC. In some embodiments, the sidewall 112 of theplatform 110 may also contact the particle P to release the particle Pfrom the electrostatic chuck ESC, such that a contact area of theplatform 110 may be increased.

As shown in FIG. 1 , the vacuum source 160 is in gaseous communicationwith the exhaust duct 142 for providing suction force through theexhaust duct 142. Hence, the particle P on the electrostatic chuck ESCmay be drawn into the vacuum source 160 either directly or after theparticle P is released from the electrostatic chuck ESC by the platform110. On the other hand, the vacuum source 160 may also help filter outthe particle P in the processing chamber where the electro static chuckESC is positioned, such that the risk of particle contamination may bereduced. Further, the particle P may be trapped after being sucked intothe vacuum source 160 for preventing the particle P from contaminatingthe electrostatic chuck ESC again.

As shown in FIG. 1 , a pair of height sensors 150 is located on thecasing 140, adjacent to the sidewall 112 of the platform 110, andcommunicated with the motor 130. The height sensors 150 can detectheight of an object (i.e., dimension along the first direction 132).Hence, the height sensors 150 may detect the distance D1 between the topsurface 114 of the platform 110 and the electrostatic chuck ESC.Further, when the distance D1 falls within an appropriate range asdescribed above, a corresponding detection signal(s) may be sent by theheight sensors 150 to the motor 130, such that the motor 130 maintainsthe distance D1 for enabling the platform 110 to release the particle Pfrom the electrostatic chuck ESC and for preventing collision betweenthe platform 110 and the electrostatic chuck ESC. In some embodiments,the height sensors 150 may have a sensing area 152 for detecting thedistance D1 and the adjacent area of the electrostatic chuck ESC tocheck whether the particle P appears thereon. It is noted that theconfiguration of the height sensors 150 may be changed based on variousdesigns, e.g., one of the height sensors 150 may be selectively omitted,more numbers of the height sensors 150 may be positioned around thecasing 140, or the height sensors 150 may be positioned near theuppermost portion of the casing 140.

Reference is made to FIG. 2A, which is a schematic diagram illustratingan optical inspection instrument 170 of the electrostatic chuck cleaningtool 100 in accordance with some embodiments of the present disclosure.In some embodiments, the optical inspection instrument 170 iscommunicated with the motor 130 and configured to detect contamination,such as the particle P, on the protrusions PT of the electrostatic chuckESC. Consequently, the optical inspection instrument 170 may determinewhether a contamination like the particle P is present on theelectrostatic chuck ESC and further detect a location of the particle Pon the electrostatic chuck ESC.

As shown in FIG. 2A, the optical inspection instrument 170 is spacedapart from the electrostatic chuck ESC. When a dummy photomask DR isattached onto the electrostatic chuck ESC, the optical inspectioninstrument 170 may transmit radiation toward the dummy photomask DR andreceive a reflection of the radiation from the dummy photomask DR.Subsequently, the optical inspection instrument 170 may analyze thetransmitted and reflected radiation. In some embodiments, the opticalinspection instrument 170 may check whether an intensity of thereflected radiation is within a predetermined range, such as about 95%to about 100% of the intensity of the transmitted radiation. When theparticle P is present between the electrostatic chuck ESC and the dummyphotomask DR, deformation of the dummy photomask DR may occur, such thatthe deformed area may not successfully reflect the transmitted radiationback to the optical inspection instrument 170. In other words, thetransmitted radiation may be deflected to other places rather than backto the optical inspection instrument 170. Hence, the intensity of thereflected radiation from the deformed area may be significantly lowered.More specifically, when the intensity of the reflected radiation from anarea on the dummy photomask DR is smaller than about 95%, it may beassumed that the area on the dummy photomask DR is a deformed area wherethe particle P is present.

Reference is made to FIG. 2B, which is a line chart depicted accordingto FIG. 2A. More specifically, the line chart of FIG. 2B and theschematic diagram of the optical inspection instrument 170 of FIG. 2Amay collectively illustrate how the detection functions. Regarding theline chart, the vertical axis therein represents the intensity of thereflected radiation, and the horizontal axis therein represents thelocation on the dummy photomask DR. The optical inspection instrument170 may transmit radiation to the dummy photomask DR and receivereflected radiation. Each location on the dummy photomask DR may have acorresponding intensity of the reflected radiation, such that acontinuous line may be presented in the line chart for indicating thecorrelation between the location on the dummy photomask DR and theintensity of the reflected radiation. When no location on the dummyphotomask DR is deformed, the intensity of the reflected radiation maybe substantially the same as that of the transmitted radiation, e.g.,the intensity of the reflected radiation may range between about 95% andabout 100%. Conversely, when a particular location on the dummyphotomask DR is deformed, the intensity of the reflected radiation maybe decreased, e.g., the intensity of the reflected radiation may besmaller than about 95%. Hence, the location of the particle P may beobviously detected according to the line chart.

In some embodiments, the optical inspection instrument 170 may recordthe location of the particle P. Subsequently, through the communicationbetween the optical inspection instrument 170 and the motor 130, theelectrostatic chuck cleaning tool 100 may move toward the recordedlocation for improving the cleaning performance and efficiency.

Reference is made to FIG. 3A, which is a schematic diagram illustratinganother scenario of an operation of the optical inspection instrument170 of the electrostatic chuck cleaning tool 100 in accordance with someother embodiments of the present disclosure. As shown in FIG. 3A, theoptical inspection instrument 170 is spaced apart from the electrostaticchuck ESC, but the dummy photomask DR (as shown in FIG. 2A) is absentfrom between the optical inspection instrument 170 and the electrostaticchuck ESC. The optical inspection instrument 170 may transmit radiationdirectly onto the electrostatic chuck ESC and receive a reflection ofthe radiation from the electrostatic chuck ESC. Subsequently, theoptical inspection instrument 170 may analyze the transmitted andreflected radiation. In some embodiments, the optical inspectioninstrument 170 may compare a detected intensity with a predeterminedstandard intensity with respect to the reflected radiation for checkingif a difference therebetween at a location falls within a predeterminedrange, such as about 0% to about 5%. When the difference at a locationis greater than about 5%, it may be assumed that the location on theprotrusions PT of the electrostatic chuck ESC is contaminated by theparticle P since the intensity of the reflected radiation may bedecreased by the particle P.

Reference is made to FIG. 3B, which is a line chart depicted accordingto FIG. 3A. More specifically, the line chart of FIG. 3B and theschematic diagram of the optical inspection instrument 170 of FIG. 3Amay collectively illustrate how the detection functions. Regarding theline chart, the vertical axis therein represents the intensity of thereflected radiation and the horizontal axis therein represents thelocation on the electrostatic chuck ESC. Each location on theelectrostatic chuck ESC may have a corresponding intensity of thereflected radiation, such that a continuous line may be presented in theline chart. The dotted line may represent the connection between thedetected intensities of the reflected radiation. The solid line mayrepresent the connection between the standard intensities of thereflected radiation. Since the particle P may deflect the transmittedradiation, the intensity of the reflected radiation from an area wherethe particle P is present may be substantially decreased. Hence, thelocation of the particle P may be adequately detected by comparing thedetected intensity with the standard intensity. For example, when adifference between the detected and standard intensities at a locationranges between about 0% and about 5%, the location may be deemed normal.When a difference at a location is greater than about 5%, it may beassumed that the location is contaminated by the particle P.

Reference is made back to FIG. 1 . The sidewall 112 and/or the topsurface 114 of the platform 110 may directly contact the particle Pwithout contacting the electrostatic chuck ESC. For example, theparticle P may be physically released from the electrostatic chuck ESCand pushed outwardly toward the casing 140 through the rotation of theplatform 110. Subsequently, the suction force provided by the vacuumsource 160 may help collect the particle P into the vacuum source 160through the exhaust duct 142. Hence, the particle P on the electrostaticchuck ESC may be fully removed. In some embodiments, the platform 110may include a high friction material like an abrasive, such that theplatform 110 may have a high friction surface to allow the particle P tobe easily released from the electrostatic chuck ESC by the rotation ofthe platform 110.

Reference is made to FIG. 4 , which is a schematic diagram illustratinga front view of an electrostatic chuck cleaning tool 100 a in accordancewith some embodiments of the present disclosure. Since some componentsof FIG. 4 are similar to those corresponding components of FIG. 1 ,descriptions for those similar components will not be repeatedhereinafter. As shown in FIG. 4 , the platform 110 may include anadhesive material 115 thereon which is configured to adhere to theparticle P on the electrostatic chuck ESC. In some embodiments, theadhesive material 115 is coated on the sidewall 112 and the top surface114 of the platform 110. Due to the configuration of the adhesivematerial 115, after the adhesive material 115 is in direct contact withthe particle P, the particle P may be subsequently taken away from theelectrostatic chuck ESC through the rotation of the platform 110. It isnoted that the configuration of the adhesive material 115 is not limitedby the present embodiment, e.g., the platform 110 may be made of theadhesive material 115.

Reference is made to FIG. 5 , which is a schematic diagram illustratinga front view of an electrostatic chuck cleaning tool 100 b in accordancewith some embodiments of the present disclosure. Since some componentsof FIG. 5 are similar to those corresponding components of FIG. 1 ,descriptions for those similar components will not be repeatedhereinafter. As shown in FIG. 5 , the platform 110 may include anultrasound generator 116 therein which is configured to emit anultrasound for separating the particle P from the electrostatic chuckESC. Due to the configuration of the ultrasound generator 116, when theplatform 110 is close to or in contact with the particle P, theultrasound provided by the ultrasound generator 116 may induceoscillation of the particle P and thus decrease the adhesion between theparticle P and the electrostatic chuck ESC. In this way, the particle Pcan be released from the electrostatic chuck ESC. Hence, the particle Pmay be removed from the electrostatic chuck ESC much easier. That is,the particle P may directly fall down due to the ultrasound vibration ormay be easier to be physically released by the rotation of the platform110.

Reference is made to FIG. 6 , which is a schematic diagram illustratinga front view of an electrostatic chuck cleaning tool 100 c in accordancewith some embodiments of the present disclosure. Since some componentsof FIG. 6 are similar to those corresponding components of FIG. 1 ,descriptions for those similar components will not be repeatedhereinafter. As shown in FIG. 6 , the platform 110 may include a lightsource 117 and a photo-catalyst material 118. In some embodiments, thelight source 117 is positioned in the platform 110 and thephoto-catalyst material 118 is located on the light source 117, suchthat the photo-catalyst material 118 may be agitated through irradiationof the light source 117 for photo-degrading the particle P. In someembodiments, the type of the light source 117 may be selected to copewith a particular type of particle contaminations. For example, a lightsource with a 254 nm wavelength may be used to photo-degradecontamination like TiO₂, or a light source with a 365 nm wavelength maybe used to photo-degrade contamination like SnO₂. It is noted that thetype of the light source 117 and the type of the photo-catalyst material118 may be selected to collectively cope with different types ofcontamination based on various designs.

It is noted that the adhesive material 115, the ultrasound generator116, and the light source 117 together with the photo-catalyst material118 may be selectively applied to the platform 110 based on variousdesigns. In some embodiments, the adhesive material 115 and theultrasound generator 116 may be together applied to the platform 110,such that after the adhesion between the particle P and theelectrostatic chuck ESC is substantially decreased by the ultrasoundvibration, it is easier to move the particle Pin contact with theadhesive material 115. In some embodiments, when at least one of theadhesive material 115, the ultrasound generator 116, and the lightsource 117 together with the photo-catalyst material 118 is individuallyor collectively utilized, the platform 110 may be rotated by the motor130 at the same time, such that the particle removing performance may befurther enhanced.

Reference is made to FIGS. 7A-7C, which are schematic diagramsillustrating various cleaning paths of the electrostatic chuck cleaningtool 100 in accordance with some embodiments of the present disclosure.A surface of the electrostatic chuck ESC may have a plurality ofprotrusions PT thereon and a plurality of channels CN between theprotrusions PT. Additionally, the protrusions PT of the electrostaticchuck ESC may be in direct contact with a backside of a photomask so asto hold the photomask.

In some embodiments, as shown in FIG. 7A, the cleaning path P1 viewedfrom the bottom direction toward the electrostatic chuck ESCsubstantially resembles a straight-line course extending vertically. Indetail, the cleaning path P1 passes through the protrusions PT of theelectrostatic chuck ESC, such that the electrostatic chuck cleaning tool100 may move along a plurality of vertical straight lines that arespaced apart from each other. Further, the moving directions of everytwo adjacent vertical straight lines are opposite to each other. Forexample, the protrusions PT of the electrostatic chuck ESC are arrangedin rows and columns, the cleaning path P1 in FIG. 7A indicates that theelectrostatic chuck cleaning tool 100 passes through a first column ofthe protrusions PT in one direction (e.g., downward direction shown inFIG. 7A) and then passes through a second column of the protrusions PTin an opposite direction (e.g., upward direction shown in FIG. 7A), andthen repeats similar movements past other columns of the protrusions PT.

In some embodiments, as shown in FIG. 7B, the cleaning path P2 viewedfrom the bottom direction toward the electrostatic chuck ESCsubstantially resembles a straight-line course extending horizontally.In detail, the cleaning path P2 passes through the protrusions PT of theelectrostatic chuck ESC, such that the electrostatic chuck cleaning tool100 may move along a plurality of horizontal straight lines that arespaced apart from each other. Further, the moving directions of everytwo adjacent horizontal straight lines are opposite to each other. Forexample, the cleaning path P2 in FIG. 7B indicates that theelectrostatic chuck cleaning tool 100 passes through a first row of theprotrusions PT in one direction (e.g., leftward direction shown in FIG.7B) and then passes through a second row of the protrusions PT in anopposite direction (e.g., rightward direction shown in FIG. 7B), andthen repeats similar movements past other rows of the protrusions PT.

In some embodiments, as shown in FIG. 7C, the cleaning path P3 viewedfrom the bottom direction toward the electrostatic chuck ESCsubstantially resembles a spiral-line course. In detail, the spiralcleaning path P3 may pass through the protrusions PT of theelectrostatic chuck ESC, such that the electrostatic chuck cleaning tool100 may move along a spiral line. Further, the moving direction of thespiral line may start from substantially the center of the electrostaticchuck ESC and then spirally spread out.

Due to the arrangement of the cleaning path, the electrostatic chuckcleaning tool 100 may clean substantially all protrusions PT ofelectrostatic chuck ESC that may be in contact with the photomask. It isnoted that the cleaning path is not limited by the aforementionedembodiments. For example, the cleaning path may be combinations of theaforementioned paths for adapting to various position arrangements ofthe protrusions PT of the electrostatic chuck ESC.

Each of the methods presented below is merely an example, and notintended to limit the present disclosure beyond what is explicitlyrecited in the claims. Additional operations can be provided before,during, and after each of the methods, and some operations described canbe replaced, eliminated, or moved around for additional embodiments ofthe processes. For clarity and ease of explanation, some elements of thefigures have been simplified.

Reference is made to FIG. 8 , which is a flow chart illustrating amethod for cleaning particle on an electrostatic chuck in accordancewith some embodiments of the present disclosure. For illustrationpurposes, the electrostatic chuck cleaning tool 100 shown in FIG. 1 isreferenced to collectively describe the details of the method.

The operation S10 a includes placing a dummy photomask DR on anelectrostatic chuck ESC. More specifically, as shown in FIG. 2A, whenthe dummy photomask DR is attached onto the electrostatic chuck ESC witha contamination like the particle P being present thereon, the dummyphotomask DR may be deformed by the particle P between the dummyphotomask DR and the electrostatic chuck ESC, such that a deformed areamay be formed by the particle P.

The operation S10 b is performed for detecting a particle P on theelectrostatic chuck ESC through the dummy photomask DR. Morespecifically, the detection may be conducted through a variety of means,such as the analysis of radiation intensity, to identify the particlelocation. More detailed descriptions of the detection are presentedbelow.

Reference is made to the FIG. 9 , which is a flow chart of the operationS10 b of FIG. 8 in accordance with some embodiments of the presentdisclosure. The operation S10 b may substantially include multipleoperations S11 b to S15 b therein.

The operation S11 b is performed for irradiating the dummy photomask DR.More specifically, as shown in FIG. 2A, the optical inspectioninstrument 170 may transmit a radiation to the dummy photomask DR andthen receive the reflected radiation from the dummy photomask DR throughdifferent components of the optical inspection instrument 170. After theradiation is transmitted and received a plurality of times, fulldetection of the dummy photomask DR is possible. In some embodiments,the radiation may be transmitted and received through the same componentof the optical inspection instrument 170.

On the other hand, in some embodiments, the optical inspectioninstrument 170 may be stationary during detection while theelectrostatic chuck ESC may be movable during detection, such that theentire dummy photomask DR on the electrostatic chuck ESC can be detectedthrough the movement of the electrostatic chuck ESC. In someembodiments, the electrostatic chuck ESC may be stationary duringdetection and the optical inspection instrument 170 may be movableduring detection to detect the entire dummy photomask DR. Hence, theoptical inspection instrument 170 and the electrostatic chuck ESC may bemoved relative to each other during detection. In some embodiments, thedetection path is substantially a straight-line course (e.g., similar tothe straight-line course of the cleaning path as shown in FIG. 7A or7B), a spiral-line course (e.g., similar to the spiral-line course ofthe cleaning path as shown in FIG. 7C), or combinations thereof, whichmay be substantially the same as the cleaning paths described above.

The operation S13 b includes analyzing a reflection of the radiation. Insome embodiments, the optical inspection instrument 170 may checkwhether an intensity of the reflected radiation is within apredetermined range, such as about 95% to about 100% of the intensity ofthe transmitted radiation. As shown in FIG. 2B, regarding the linechart, the vertical axis therein may represent the intensity of thereflected radiation and the horizontal axis therein may represent thelocation on the dummy photomask DR. As described above, the particle Ppresent between the electrostatic chuck ESC and the dummy photomask DRmay lower the intensity of the reflected radiation. Therefore, when theintensity of the reflected radiation from an area on the dummy photomaskDR is smaller than about 95%, it may be assumed that this area on thedummy photomask DR is a deformed area where the particle P is present.

The operation S15 b includes determining whether the particle P ispresent on the electrostatic chuck ESC based on the analyzation of thereflection of the radiation. More specifically, based on the analyzationresult from the operation S13 b as discussed above, the existence of theparticle P may be identified through checking if the intensity of thereflection is within the predetermined range. Additionally, based onwhere the radiation is reflected, a location of the particle P may bedetected and further recorded, so as to facilitate the followingoperations.

Reference is now made back to FIG. 8 . The operation S10 c includesremoving the dummy photomask DR from the electrostatic chuck ESC. Morespecifically, after the operation S13 b of identifying the location ofthe particle P, the dummy photomask DR may be removed from theelectrostatic chuck ESC, such that subsequent cleaning processes of theelectrostatic chuck ESC may be conveniently performed.

The operation S10 d includes moving a platform 110 close to theelectrostatic chuck ESC. More specifically, the operation S10 d isperformed when the determination from the operation S15 b abovedetermines that the particle P is present on the electrostatic chuckESC. In some embodiments, the electrostatic chuck cleaning tool 100 maybe movable and the electrostatic chuck ESC is stationary during movementof the electrostatic chuck cleaning tool 100, such that the platform 110may be moved close to the particle P on the electrostatic chuck ESC toallow for interactions to take place between the platform 110 and theelectrostatic chuck ESC. In some embodiments, the electrostatic chuckESC is movable and the electrostatic chuck cleaning tool 100 isstationary during movement of the electrostatic chuck ESC for moving theelectrostatic chuck ESC close to the platform 110. Hence, theelectrostatic chuck cleaning tool 100 and the electrostatic chuck ESCmay be moved relative to each other.

The operation S10 e includes separating the platform 110 from theelectrostatic chuck ESC by a distance D1. In some embodiments, the motor130 may move the platform 110 toward the electrostatic chuck ESC and mayrefrain from rotating the platform 110 until a distance D1 between theplatform 110 and the electrostatic chuck ESC falls within an appropriaterange, e.g., the distance D1 may be in a range between about 100 um andabout 10 nm. If the distance D1 is smaller than about 10 nm, a collisionbetween the platform 110 and the electrostatic chuck ESC may occur.Conversely, if the distance D1 is greater than about 100 um, theplatform 110 may not interact with the particle P. Additionally, as soonas rotation of the platform 110 is started, the distance D1 may be keptsubstantially the same, such that the collision between the platform 110and the electrostatic chuck ESC may be prevented and the platform 110may contact the particle P.

The operation S10 f includes cleaning the particle P on theelectrostatic chuck ESC without contacting the electrostatic chuck ESC.More specifically, the interactions between the platform 110 and theelectrostatic chuck ESC for releasing the particle P may include variousmeans as described below.

In some embodiments, the operation S10 f may include rotating theplatform 110 to release the particle P from the electrostatic chuck ESC.As shown in FIG. 1 , the sidewall 112 and/or the top surface 114 of theplatform 110 may directly contact the particle P without touching theelectrostatic chuck ESC. Hence, the particle P may be physicallyreleased from the electrostatic chuck ESC and pushed outwardly towardthe casing 140 through the rotation of the platform 110.

In some embodiments, the operation S10 f may include adhering to theparticle P through an adhesive material 115 on the platform 110 torelease the particle P from the electrostatic chuck ESC. As shown inFIG. 4 , the adhesive material 115 may adhere to the particle P on theelectrostatic chuck ESC. After the adhesive material 115 is in directcontact with the particle P, the particle P may be subsequently releasedfrom the electrostatic chuck ESC due to movement of the platform 110,such as the linear movement and/or the rotation thereof.

In some embodiments, the operation S10 f may include vibrating theparticle P through an ultrasound emitted from the platform 110 torelease the particle P from the electrostatic chuck ESC. As shown inFIG. 5 , the ultrasound generator 116 may emit ultrasound toward theparticle P on the electrostatic chuck ESC. Subsequently, when theplatform 110 is close to or in contact with the particle P, theultrasound may decrease the adhesion between the particle P and theelectrostatic chuck ESC and thus release the particle P from theelectrostatic chuck ESC. Hence, the particle P may be removed from theelectrostatic chuck ESC much easier. In other words, the particle P maydirectly fall down due to the ultrasound vibration or may be easier tobe physically released by the rotation of the platform 110.

In some embodiments, with reference to FIG. 6 , the operation S10 f mayinclude photo-degrading the particle P through the photo-catalystmaterial 118 on the platform 110 to release the particle P from theelectrostatic chuck ESC. The photo-catalyst material 118 may be agitatedthrough irradiation of the light source 117. After the photo-catalystmaterial 118 is stimulated by the light source 117, the photo-catalystmaterial 118 may be moved to contact the particle P and thenphoto-degrade the particle P. In some embodiments, the type of the lightsource 117 may be selected to cope with a particular type of particlecontaminations as described above.

In some embodiments, the operation S10 f may include vacuuming theelectrostatic chuck ESC. More specifically, the vacuum source 160 mayprovide suction force for drawing the particle P into the vacuum source160 through the exhaust duct 142. In some embodiments, the vacuum source160 may directly draw the particle P into the vacuum source 160. In someembodiments, the vacuum source 160 may function together with thevarious means for cleaning the particle P as described above forenhancing the cleaning performance. Since the vacuum source 160 may trapthe released particle P, the particle P is prevented from contaminatingthe electrostatic chuck ESC again. In some embodiments, the suctionforce is provided by the vacuum source 160 to between the electrostaticchuck ESC and the platform 110 after the particle P is released from theelectrostatic chuck ESC by the above-mentioned various means, such thatthe particle P may be removed from the electrostatic chuck ESC and thencollected in the vacuum source 160. In some embodiments, the suctionforce is provided when the electrostatic chuck cleaning tool 100functions, such that potential damage on the electrostatic chuck ESCcaused by the particle P from the electrostatic chuck cleaning tool 100may be decreased.

Furthermore, in some embodiments, the operation S10 f may be performedalong a cleaning path that is substantially a straight-line course, aspiral-line course, or combinations thereof as illustrated in FIGS. 7Ato 7C. Hence, substantially every protrusion PT on the electrostaticchuck ESC that may contact the photomask can be cleaned. In someembodiments, the detected path in the operation S11 b may besubstantially the same as the cleaning path, such that the electrostaticchuck cleaning tool 100 may conduct a more precise cleaning operationtoward the area where the particle P is detected.

Reference is made to FIG. 10 , which is a flow chart illustrating amethod for cleaning particle on an electrostatic chuck in accordancewith some other embodiments of the present disclosure. For illustrationpurposes, the electrostatic chuck cleaning tool 100 is referenced tocollectively describe the details of the method as presented below.

The operation S20 a includes irradiating an electrostatic chuck ESC.More specifically, as shown in FIG. 3A, the optical inspectioninstrument 170 may transmit a radiation directly to the electrostaticchuck ESC and receive the reflected radiation from the electrostaticchuck ESC for scanning the electrostatic chuck ESC. Similarly, theelectrostatic chuck ESC and the optical inspection instrument 170 may bemoved relative to each other to allow for irradiating the entireelectrostatic chuck ESC.

The operation S20 b includes analyzing a reflection of the radiation.More specifically, as shown in FIG. 3B, the optical inspectioninstrument 170 may compare a detected intensity (represented by thedotted line) with a standard intensity (represented by the solid line)with respect to the reflected radiation. Subsequently, the opticalinspection instrument 170 may check whether a difference between thedetected intensity and the standard intensity at a location falls withina predetermined range, such as about 0% to about 5%. When the differenceat a location is greater than about 5%, it may be assumed that thelocation on the electrostatic chuck ESC is contaminated by the particleP since the intensity of the reflected radiation may be decreased by theparticle P.

The operation S20 c includes determining whether the particle P ispresent on the electrostatic chuck ESC based on the reflection of theradiation transmitted by the optical inspection instrument 170. Morespecifically, based on the analyzation result from the operation S20 bas discussed above, the existence of the particle P may be determinedthrough comparing the real intensity with the standard intensity withrespect to each reflected radiation.

The operation S20 d includes recording a location of the particle P onthe electrostatic chuck ESC when the determination from the operationS20 c as discussed above determines that the particle P is present onthe electrostatic chuck ESC. In some embodiments, after theelectrostatic chuck ESC is irradiated and the location of the particle Pis identified, the optical inspection instrument 170 may record thelocation, such that the electrostatic chuck cleaning tool 100 mayenhance the cleaning to the location as described below.

The operation S20 e includes moving a platform 110 close to the locationof the particle P. In some embodiments, through the communicationbetween the optical inspection instrument 170 and the motor 130, themotor 130 may move the platform 110 toward the recorded location of theparticle P. In some embodiments, when multiple locations are recorded,the platform 110 may approach the recorded locations one by one. In someembodiments, the platform 110 may move along the cleaning path and/orthe detected path as mentioned above and then temporarily stay at therecorded location for enhancing the cleaning thereto.

The operation S20 f includes removing the particle P on theelectrostatic chuck ESC without contacting the electrostatic chuck ESC.Since some actions of the operation S20 f are similar to thecorresponding actions of the operation S10 f described above,descriptions for the similar actions will not be repeated hereinafter.

Based on the above-mentioned descriptions, various advantages may beprovided by the present disclosure. In detail, the particle on theelectrostatic chuck may be fully detected by irradiating a surface ofthe electrostatic chuck with or without a dummy photomask. A variety ofmeans for releasing the particle on the electrostatic chuck may includecontacting the particle with a rotated platform, adhering to theparticle, vibrating the particle, photo-degrading the particle, orcombinations thereof. Additionally, when at least one of the variousmeans is conducted, a vacuum source may provide suction force toindividually or collectively draw the particle into the vacuum source.Therefore, the in-situ detecting and cleaning with respect to theparticle may be achieved, such that the presence of particles on theelectrostatic chuck may be minimized. Additionally, since the particlecontamination is reduced, the machine operating time may be increased,while the costs associated with photomask damage and product reworkingmay be decreased.

In some embodiments, a method includes transmitting a radiation towardan electrostatic chuck, receiving a reflection of the radiation,analyzing the reflection of the radiation, determining whether aparticle is present on the electrostatic chuck based on the analyzingthe reflection of the radiation, and moving a cleaning tool to alocation of the particle on the electrostatic chuck when thedetermination determines that the particle is present.

In some embodiments, a method includes moving a platform of a cleaningtool toward an electrostatic chuck, releasing a particle from theelectrostatic chuck using the platform of the cleaning tool, and drawingthe particle from above the platform into an exhaust duct around theplatform using a vacuum source in gaseous communication with the exhaustduct after releasing the particle from the electrostatic chuck.

In some embodiments, a cleaning tool includes a rotatable platform, amotor, a casing, and a vacuum source. The rotatable platform has asidewall and a top surface. The motor is configured to actuate athree-dimensional movement of the rotatable platform. The casing isaround the rotatable platform and free from covering the top surface ofthe rotatable platform. The casing and the sidewall of the rotatableplatform defines an exhaust duct around the rotatable platform. Thevacuum source is connected to the exhaust duct.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A method comprising: emitting, by a first portionof an optical inspection instrument, a radiation toward a supportingsurface of a chuck, wherein the chuck is configured for fixing asemiconductor workpiece on the supporting surface, and the opticalinspection instrument faces the supporting surface; receiving, by asecond portion of the optical inspection instrument, a reflection of theradiation reflected from the chuck; analyzing the reflection of theradiation; determining whether a particle is present on the supportingsurface of the chuck based on the analyzing the reflection of theradiation; and removing the particle by using a cleaning tool comprisingan exhaust duct.
 2. The method of claim 1, wherein the chuck comprises aplurality of channels at the supporting surface of the chuck.
 3. Themethod of claim 1, wherein analyzing the reflection of the radiationcomprises comparing a spatial intensity distribution of the reflectionof the radiation with a standard spatial intensity distribution.
 4. Themethod of claim 1, wherein analyzing the reflection of the radiationcomprises checking whether an intensity of the reflection is within apredetermined range.
 5. The method of claim 1, further comprising:placing a dummy photomask on the supporting surface of the chuck,wherein emitting the radiation toward the supporting surface of thechuck comprises emitting the radiation to the dummy photomask.
 6. Themethod of claim 1, wherein removing the particle comprises generating asuction force through the exhaust duct.
 7. The method of claim 6,further comprising moving the exhaust duct in a circle path whengenerating the suction force.
 8. A method comprising: providing acleaning tool comprising: a vacuum source; and an exhaust ductcomprising a first portion and a second portion connected to the firstportion, wherein the first portion and the second portion extend indifferent directions; and generating, by using the vacuum source, asuction force in the exhaust duct; and moving the cleaning tool toward asurface of a chuck.
 9. The method of claim 8, wherein the first portionand the second portion of the exhaust duct form a substantially rightangle therebetween.
 10. The method of claim 8, wherein the exhaust ductfurther comprises a third portion between the second portion and thevacuum source.
 11. The method of claim 10, wherein the first portion andthe third portion of the exhaust duct extend in substantially the samedirection.
 12. The method of claim 8, wherein the chuck comprises aplurality of protrusions on the surface.
 13. The method of claim 8,further comprising detecting whether a particle is on the surface of thechuck prior to moving the cleaning tool toward the surface of the chuck.14. The method of claim 8, wherein the chuck is an electrostatic chuck.15. A method comprising: moving an optical inspection instrument towarda surface of a chuck; detecting, by using the optical inspectioninstrument, a location of a particle on the surface of the chuck; afterdetecting the location of the particle, moving the optical inspectioninstrument away from the surface of the chuck; after moving the opticalinspection instrument away from the surface of the chuck, moving acleaning tool toward the location of the particle; and removing theparticle by using the cleaning tool.
 16. The method of claim 15, whereinmoving the cleaning tool toward the location of the particle comprisesmoving the cleaning tool in a circle path.
 17. The method of claim 15,wherein detecting the location of the particle on the surface of thechuck comprises analyzing a reflection of radiation transmitted from theoptical inspection instrument to the surface of the chuck with astandard intensity of the reflection of the radiation.
 18. The method ofclaim 15, wherein removing the particle comprises generating an exhaustflow in the cleaning tool to remove the particle.
 19. The method ofclaim 15, wherein the surface has channels.
 20. The method of claim 15,further comprising rotating the cleaning tool when removing theparticle.